Several different processes for producing powdered metal products have been developed and are currently being used to produce metal powders having certain characteristics, such as increased densities and increased flowabilities, that are desirable in subsequent metallurgical processes, such as, for example, sintering and plasma-spraying processes.
One process, known as plasma-based densification, involves contacting a metal precursor material with a hot plasma jet. The hot plasma jet liquefies and/or atomizes the metal in order to form small, generally spherically shaped particles. The particles are then allowed to re-solidify before being recovered. The resulting powdered metal product is often characterized by having a high flowability and high density, thereby making the powdered metal product desirable for use in subsequent processes (e.g., sintering and plasma-spraying).
Unfortunately, however, plasma-based densification processes are not without their drawbacks. For example, plasma-based densification processes tend to be expensive to implement, are energy intensive, and also suffer from comparatively low yields.
Another type of process, known as spray drying, involves a process wherein a solution or slurry containing the desired metal is rapidly dried to particulate form by atomizing the liquid in a hot atmosphere. One type of spray drying process for producing a powdered metal product utilizes a rotating atomizing disk provided in a heated process chamber. A liquid precursor material (e.g., a slurry or solution) containing a powdered metal material is directed onto the rotating disk. The liquid precursor material is accelerated generally outwardly by the rotating disk. The heated chamber speeds the evaporation of the liquid component of the liquid precursor material as the same is accelerated outwardly by the rotating disk. The resulting powdered metal end product is then collected from a perimeter wall surrounding the rotating disk.
While the foregoing spray drying process is often used to form a powdered metal product, it is not without its disadvantages. For example, spray drying processes also tend to suffer from comparatively low yields and typically result in a metal powder product having a lower density than is possible with plasma-based densification processes. Spray drying processes also involve fairly sizable apparatus (e.g., atomizing disks having diameters on the order of 10 m) and are energy intensive. The spray drying process also tends to be difficult to control, and it is not unusual to encounter some degree of variability in the characteristics of the powdered metal product, even though the process parameters remain the same. Such variability further increases the difficulty in producing a final powdered metal product having the desired characteristics.
Consequently, a need remains for a system capable of producing a powdered metal end product having characteristics, such as high density and high flowability, that make the powdered metal end product more desirable for use in subsequent applications. Ideally, such a system should be capable of producing increased yields of powdered metal end product, while at the same time involving less complexity, energy, and expense when compared to conventional processes.